Steam wetness measurement with microwave tomography

Abstract

A system for measuring steam wetness, including: a plurality of microwave sensors for detecting microwave signals passing through a supply of steam flowing through a cavity; a calibration system for calibrating the plurality of microwave sensors; a film measurement system for measuring a characteristic of a film flowing along an inner surface of the cavity; a system for determining a characteristic of the steam flowing through the cavity based on data provided by the plurality of microwave sensors; and a system for determining a wetness of the steam flowing through the cavity based on the characteristic of the steam flowing through the cavity and the characteristic of the film flowing along the inner surface of the cavity.

What is claimed is: 
     
       1. A system for measuring steam wetness, comprising:
 a plurality of microwave sensors for detecting microwave signals passing through a supply of steam flowing through a cavity; 
 a film measurement system for measuring a characteristic of a film flowing along inner surface of the cavity; 
 a system for determining a characteristic of the steam flowing through the cavity based on data provided by the plurality of microwave sensors; 
 a system for determining a wetness of the steam flowing through the cavity based on the characteristic of the steam flowing through the cavity and the characteristic of the film flowing along the inner surface of the cavity; and 
 a calibration system for calibrating the plurality of microwave sensors, the calibration system obtaining phase shift and attenuation measurements over a range of frequencies using the plurality of microwave sensors. 
 
     
     
       2. The system for measuring steam wetness according to  claim 1 , wherein the cavity comprises a pipe. 
     
     
       3. The system for measuring steam wetness according to  claim 1 , wherein the plurality of microwave sensors are distributed about a circumference of the cavity. 
     
     
       4. The system for measuring steam wetness according to  claim 3 , further comprising a plurality of sets of microwave sensors, wherein each set of microwave sensors is disposed at a different location along the cavity and obtains the microwave signals at that location. 
     
     
       5. The system for measuring steam wetness according to  claim 4 , wherein the system for determining the wetness of the steam flowing through the cavity determines the characteristic of the steam at each different location of the sets of microwave sensors along the cavity. 
     
     
       6. The system for measuring steam wetness according to  claim 5 , wherein the system for determining the wetness of the steam flowing through the cavity cross-correlates the characteristic of the steam determined at each different location. 
     
     
       7. The system for measuring steam wetness according to  claim 1 , wherein the characteristic of the film on the inner surface of the cavity comprises at least one of a thickness of the film and a flow velocity of the film. 
     
     
       8. The system for measuring steam wetness according to  claim 1 , wherein the characteristic of the steam flowing through the cavity comprises a void fraction of the steam. 
     
     
       9. The system for measuring steam wetness according to  claim 1 , further comprising a system for modifying the characteristic of the steam based on the determined characteristic of the film. 
     
     
       10. The system for measuring steam wetness according to  claim 1 , wherein the film measurement system comprises at least one electrode for detecting a conductivity of the film. 
     
     
       11. The system for measuring steam wetness according to  claim 1 , wherein the plurality of microwave transducers extend into an interior of the cavity beyond, and isolated from, the film. 
     
     
       12. A method for measuring steam wetness, comprising:
 detecting, using a plurality of microwave sensors, microwave signals passing through a supply of steam flowing through a pipe; 
 measuring a characteristic of a film flowing along an inner surface of the pipe; 
 determining a characteristic of the steam flowing through the pipe based on data provided by the plurality of microwave sensors; 
 determining a wetness of the steam flowing through the pipe based on the characteristic of the steam flowing through the pipe and the characteristic of the film on the inner surface of the pipe; and 
 calibrating the plurality of microwave sensors prior to the detecting, the calibrating including obtaining phase shift and attenuation measurements over a range of frequencies using the plurality of microwave sensors. 
 
     
     
       13. The method for measuring steam wetness according to  claim 12 , wherein the characteristic of the film comprises at least one of a thickness of the film and a flow velocity of the film. 
     
     
       14. The method for measuring steam wetness according to  claim 12 , wherein the characteristic of the steam flowing through the pipe comprises a void fraction of the steam. 
     
     
       15. The method for measuring steam wetness according to  claim 12 , wherein the plurality of microwave transducers extend into an interior of the pipe beyond, and isolated from, the film. 
     
     
       16. The method for measuring steam wetness according to  claim 12 , wherein the detecting further comprises detecting, at a plurality of different locations along the pipe, the microwave signals passing through the supply of steam flowing through the pipe, and wherein the determining the wetness of the steam flowing through the pipe further comprises cross-correlating the characteristic of the steam determined at each of the plurality of different locations. 
     
     
       17. The method for measuring steam wetness according to  claim 16 , further comprising modifying the characteristic of the steam based on the determined characteristic of the film. 
     
     
       18. A combined cycle power generation system, comprising:
 a gas turbine system; 
 a steam turbine system powered by steam generated using exhaust gases from the gas turbine system; and 
 a system for measuring a wetness of the steam, including:
 a plurality of microwave sensors for detecting microwave signals passing through a supply of steam flowing through a pipe; 
 a calibration system for calibrating the plurality of microwave sensors; 
 a film measurement system for measuring a characteristic of a film flowing along inner surface of the pipe; 
 a system for determining a characteristic of the steam flowing through the pipe based on data provided by the plurality of microwave sensors; 
 
 a system for determining a wetness of the steam flowing through the pipe based on the characteristic of the steam flowing through the pipe and the characteristic of the film flowing along the inner surface of the pipe; and
 a calibration system for calibrating the plurality of microwave sensors, the calibration system obtaining phase shift and attenuation measurements over a range of frequencies using the plurality of microwave sensors.